With advancement of IT technologies, a variety of small-sized hand-and-palm-held portable information devices have come out in the world. Those portable information devices are small size and light weight and therefore extremely convenient to carry, and at the present not only mobile phones but also PDAs, smart phones, portable game machines and UMPCs (Ultra Mobile PCs) are consecutively put on the market.
For example, the following are the Patent documents as technologies disclosed at the present.    [Patent document 1] Japanese Patent Laid-Open Publication No. 2001-306291    [Patent document 2] Japanese Patent Laid-Open Publication No. 2003-162355